Sex Modifies Acute Ozone-Mediated Airway Physiologic Responses.

Sex differences clearly exist in incidence, susceptibility, and severity of airway disease and in pulmonary responses to air pollutants such as ozone (O3). Prior rodent O3 exposure studies demonstrate sex-related differences in the expression of lung inflammatory mediators and signaling. However, whether or not sex modifies O3-induced airway physiologic responses remains less explored. To address this, we exposed 8-10 week old male and female C57BL/6 mice to either 1 or 2 ppm O3 or filtered air (FA) for 3 h. At 12, 24, 48 and 72h following exposure, we assessed airway hyperresponsiveness (AHR) to methacholine (MCh), bronchoalveolar lavage (BAL) fluid cellularity, cytokines and total protein/albumin, serum progesterone and whole lung immune cells by flow cytometry. Male mice generated consistent AHR to methacholine at all timepoints following exposure. Alternatively, females had less consistent airway physiologic responses to MCh, which were more variable between individual experiments and did not correlate with serum progesterone levels. Bronchoalveolar lavage fluid total cells peaked at 12h and were persistently elevated through 72h. At 48h, BAL cells were greater in females vs males. Bronchoalveolar lavage fluid cytokines and total protein/albumin increased following O3 exposure without sex differences. Flow cytometry of whole lung tissue identified dynamic O3-induced immune cell changes also independent of sex. Our results indicate sex differences in acute O3-induced airway physiology responses and airspace influx without significant difference in other injury and inflammation measures. This study highlights the importance of considering sex as a biological variable in acute O3-induced airway physiology responses.